GB981184A - Improvements in or relating to frequency converter arrangements for multi-channel modulated carrier communication systems - Google Patents

Abstract

981,184. Multiplex systems; frequency changing. TELEFUNKEN A.G. March 10, 1961 [March 16, 1960], No. 8837/61. Headings H3F, H4L and H4R. In a frequency-division multiplex carrier wave transmission system the twelve speech channels LF (one shown) are each converted into a common frequency range of 20-24 kc/s. by means of an oscillator producing an output having a frequency of 20 kc/s. cooperating with a respective modulator 3, a filter 4 selecting the upper sideband in each case. The upper sidebands in the range 20-24 kc/s. are fed to respective modulators 5 of which there are twelve arranged in groups of four and supplied with carrier oscillators 112, 116, 120 and 124 kc/s. respectively in each group. The outputs of each group are combined as at 6 and after amplification at 7 a filter 8 selects the upper sidebands in each case producing three outputs in the range 132-148 kc/s. The three signal groups thus formed are fed to respective modulators 9 supplied with carrier oscillations of 208, 224 and 240 kc/s. respectively, and the outputs of these three modulators are combined at 10 and a common filter 11 selects the three lower sidebands providing an output in the range 60-108 kc/s. The receiver 13 to 24 is the inverse of the transmitting arrangement. The system permits the use of common filters 8 and 11 with consequent economy.